Biofilms of S. mutans UA159 were grown on different surfaces in BHI, CP673451 in vivo stained with LIVE/DEAD BacLight fluorescent dye and analyzed with CLSM. The panels show cross-section images of biofilms from polystyrene (A), Ti
(B), HA (C) and composite (D) materials. Dead cells were stained red, and live cells were stained green. To further determine the impact of the tested material surfaces on the physiology of the bacteria, we tested the secretion of AI-2 signal by S. mutans biofilms. As AI-2 reporter strain we used V. harveyi MM77, AZD5582 supplier which does not produce endogenous AI-1 or AI-2. Thus, any increase of its luminescence above background level is due to exogenous AI present in the growth medium. The highest effect on the luminescence of the reporter strain was of the conditioned medium taken from biofilms grown on HA with normalized fold induction ON-01910 in vivo of ~100 per 10 million cells. Conditioned media from biofilms grown on composite and polystyrene had a similar effect on the luminescence resulting in normalized fold induction of ~40. The lowest effect on the reporter strain was of the conditioned medium taken from biofilm grown on titanium with normalized fold induction of only ~10 (Figure 5). Figure 5 AI-2 signal secretion by S. mutans biofilms on different surfaces. Biofilms were grown on each material and the resulting conditioned media were exposed to V. harveyi MM77 for AI-2 bioassay.
Fold induction in luminescence of each sample was calculated above background luminescence of the negative control (sample without addition of any conditioned medium) and was normalized by the value of total fluorescence of live bacteria within the
relevant biofilm detected by CLSM. Discussion Mechanisms governing biofilm formation have generated considerable interest in the general biofilm field and also in dental-related biofilms [30–35]. Oral biofilms vary in both structure and function but share general characteristics. In order to persist within the oral ecosystem, the bacteria need to adhere to either soft or hard tissues and to overcome local shear forces. Although it is well documented that saliva constituents coat biological surfaces in the oral cavity, the principal aim of this Tolmetin study was to examine a genetic adaptation of bacteria upon immobilization on non-biological surfaces. Our results indicate that bacteria can sense their non-biological substrate and express different genes accordingly, probably as part of the adjustment to a new micro-environment. It is likely that the stressful situation conducts the bacteria to enhance the factors of successful adjustment to certain surface by activation of expression of certain combination of genes. This could explain the fact that bacteria are able to adjust to any surface by manipulating their gene expression pattern. Differences in formed biofilm depths and viabilities among the different materials might be due to their surface properties.